The Senate’s NATO Backstop Is About to Lose Its Biggest Champions

The retirements of Sens. Jeanne Shaheen and Thom Tillis could spell trouble for the Senate NATO Observer Group.

Sens. Thom Tillis and Jeanne Shaheen at an event.

Sens. Thom Tillis and Jeanne Shaheen co-chair the Senate NATO Observer Group. (Denes Erdos/AP)

Sens. Jeanne Shaheen and Thom Tillis spent eight years rebuilding a bipartisan Senate channel to NATO at a time when allies increasingly looked to Congress for stability in Washington.

Now both are leaving Congress, with no successors settled and no guarantee the group they rebuilt will survive or carry the same weight without them.

Both senators say they are trying to keep the Senate NATO Observer Group, or SNOG, active. But neither gets to choose who takes over.

“It’s not my decision. It’s not Sen. Tillis’s decision. It’s the leadership’s decision,” Shaheen, a Democrat from New Hampshire, told NOTUS in an interview.

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Their departure comes as the United States’ relationship with NATO is being tested under President Donald Trump.

Trump has pushed NATO allies to dramatically increase their defense spending, helping secure a new pledge last year for each nation to spend at least 5% of GDP by 2035. His second term has also deepened strains with the alliance, from renewed pressure for the U.S. to take over Greenland, clashes with European governments over the Iran war and moves to reduce the U.S. military presence in Europe.

Tillis described the group as a way for senators to reassure allies when Trump’s rhetoric raises doubts about the U.S.’s commitment to NATO.

“Look, you got to deal with the rhetoric. But the reality is, membership in NATO is a treaty that the president can certainly cause problems, but cannot by himself negate.” Tillis, a Republican from North Carolina, said in an interview.

Rachel Ellehuus, a former U.S. defense adviser at NATO, said the Senate group is “even more important now when we’re getting mixed messages from the executive branch.”

“A group like the SNOG really does show you where that consensus is and reminds Europeans that there are representatives on both sides of the political aisle who strongly support NATO,” said Ellehuus, now the director-general of Royal United Services Institute, a U.K. defense think tank.

Over the years, the group became a regular presence at NATO summits and other major transatlantic gatherings, giving senators direct access to allied leaders and another way to signal bipartisan support. Most recently, Shaheen led a bipartisan delegation to the July summit in Ankara, Turkey, which her office described as her final one as co-chair.

Both senators pointed to Finland’s and Sweden’s NATO accessions as major accomplishments, saying the group helped build Senate support and move the ratification process quickly after Russia invaded Ukraine.

But the group has a built-in weakness: It does not formally exist in law. It is voluntary and has repeatedly come and gone since the Senate first created it in 1997 during NATO enlargement. Shaheen and Tillis revived it again in 2018.

That history is part of why Shaheen and Tillis are trying to make the group permanent before they leave, creating a clearer structure for succession and avoiding another lapse.

The senators introduced legislation last year to codify the group, but the bill has not advanced. Tillis said he still hopes to move it through the National Defense Authorization Act or a year-end package.

“I think it’d be ideal,” Tillis said. “I’m trying to do it ahead of leaving.”

Tillis said part of the holdup is an internal Senate dispute over who should control the group. He said no one is opposed to its existence, but some senators want to determine which committees its leaders should come from, something he called “silly or petty.”

“We’ve got some people in the mix that want to lead it or kind of fold it into one committee or another, which makes no sense,” Tillis said.

Without a permanent structure, the group depends heavily on its leaders, making its future influence largely a question of who takes over. Shaheen said she and Tillis “have had a really good relationship and share the same perspective about NATO.”

“When these groups have fallen to the wayside, it’s because leaders have not invested the time,” Tillis said, adding that the group’s success is “very much personality-driven.”

“They’re all as good as the commitment of the leaders, their working relationship, their ability to get other members engaged and their willingness to travel,” he added.

Jim Townsend, a former senior Pentagon official who also served in the U.S. Mission to NATO in Brussels, said Shaheen and Tillis “leave very big shoes to fill” because of their credibility on both sides of the Atlantic and the time they have invested in NATO relationships.

Tillis and Shaheen have both pointed to Sens. Mike Rounds (R-South Dakota) and Angus King (I-Maine) as potential successors. Shaheen said Rounds and King “would be great,” but again stressed that the choice belongs to leadership. King’s office declined to comment on the matter.

Tillis has personally encouraged Rounds to consider the role and called him “probably first among all Republicans in his participation.”

Rounds said he is interested.

“I’ve indicated that I would like an opportunity to do that if it works into the bigger picture of where everybody else fits in,” he told NOTUS.

Rounds said he would be open to working with King but noted that other names have also been suggested. He said Senate leadership has not approached him about taking over.

Rounds said the next co-chairs will have to preserve the group’s bipartisan identity if they want it to have credibility overseas.

Congressional engagement carries real weight with allies because it gives them “another view about how Washington thinks” beyond the presidential administration, Townsend said.

Townsend said the group’s disappearance would leave a real gap in Congress’ NATO outreach.

“If the SNOG goes away, that takes a tool out of the toolbox,” Townsend said. “And if you don’t have a SNOG providing that kind of voice, that will certainly hurt the effort to keep the alliance going through this tough time.”